The trial was conducted in Germany, The Republic of Macedonia, Russian Federation, Serbia and South Africa. The aim of this trial was to make a safety comparison of insulin detemir produced by a new production method (NN729) with insulin detemir made by the previous production method (NN304). Subjects were treated with NN729 or NN304 for a period of 52 weeks at the same total daily dose and frequency of administration as their own pre-trial basal insulin . During the trial doses were individualised based on subject's plasma glucose measurements.